This document provides guidelines for dimensioning engineering drawings in 3 sentences: Dimensioning involves specifying an object's size, location, material, and other information using extension lines, dimension lines, leader lines, and notes to facilitate manufacturing and measurement. Key guidelines include placing dimensions outside views for clarity, using aligned or unidirectional methods for dimension figures, and noting radii, holes, chamfers, and rounded ends according to manufacturing needs. The document demonstrates best practices and common mistakes to avoid for clear and complete dimensioning of drawings.

1. UNIT 2
Dimensioning
Subject : Basics of Engineering Graphics -
Diploma Sem 2

2. Contents
Introduction
Dimensioning components
Dimensioning object’ s features
Placement of dimensions.

3. DEFINITION
Dimensioning is the process of specifying part’ s
information by using of figures, symbols and notes.
This information are such as:
1. Sizes and locations of features
2. Material’s type
3. Number required
4. Kind of surface finish
5. Manufacturing process
6. Size and geometric tolerances

4. DIMENSIONING COMPONENTS
Extension lines
Dimension lines
(with arrowheads)
Leader lines
Dimension figures
Notes :
- local note
- general note
Drawn with
4H pencil
Lettered with
2H pencil.

5. indicate the location on the object’s features that
are dimensioned.
EXTENSION LINES

6. EXTENSION LINES
Leave a visible gap (≈ 1 mm) from a view and start drawing an extension line.
Extend the lines beyond the (last) dimension line 1-2 mm.
Visible gap
COMMON MISTAKE

7. Do not break the lines as they cross object lines.
COMMON MISTAKE
Continuous
EXTENSION LINES

8. Dimension lines should not be spaced too close
to each other and to the view.
11
34
Leave a space at least
2 times of a letter height.
16
35
DIMENSION LINES
Leave a space at least
1 time of a letter height.

9. DIMENSION FIGURES
The height of figures is suggested to be 2.5~3 mm.
Place the numbers at about 1 mm above dimension
line and between extension lines.
COMMON MISTAKE
11
11
34
34

10. 16.25
16.25
or
DIMENSION FIGURES
When there is not enough space for figure or
arrows, put it outside either of the extension lines.
1
Not enough space
for figures
Not enough space
for arrows
1 1

11. The JIS and ISO standards adopt the unit of
Angular dimension in degree with a symbol “o”
place behind the figures (and if necessary
minutes and seconds may be used together).
DIMENSION FIGURES : UNITS
Length dimension in millimeters without
specifying a unit symbol “mm”.

12. 1. Aligned method
2. Unidirectional method
The dimension figures are placed so that they are readable from the
bottom and right side of the drawing.
The dimension figures are placed so that they can be read from the
bottom of the drawing.
Do not use both system on the same drawing or on the same series of
drawing (JIS Z8317)
DIMENSIONING METHOD

13. 30
30
30
30
EXAMPLE : Dimension of length using aligned method.

14. 30
30
30
30
3030
30
30
EXAMPLE : Dimension of length using unidirectional method.

15. 45o
45o
45o
45o
EXAMPLE : Dimension of angle using aligned method.

16. 45o
45o
45o
45o
45o
45o
45o
45o
EXAMPLE : Dimension of angle using unidirectional method.

17. LOCAL NOTES
Place the notes near to the feature which they
apply, and should be placed outside the view.
Always read horizontally.
10 Drill
COMMON MISTAKES
10 Drill
≈ 10mm
10Drill
Too far

18. THE BASIC CONCEPT
Dimensioning is accomplished by adding size and location information
necessary to manufacture the object and component.
Clear
Complete
Facilitate the
- manufacturing method
- measurement method
This information have to be

19. L
L
S
S
S
Designed
part
EXAMPLE
To manufacture this part
we need to know…
1. Width, depth and
thickness of the part.
2. Diameter and depth
of the hole.
3. Location of the holes.
“S” denotes size dimension.
“L” denotes location dimension.
S
L
L

20. ANGLE
To dimension an angle use circular dimension
line having the center at the vertex of the angle.
COMMON MISTAKE

21. FILLETS AND ROUNDS
Give the radius of a typical fillet only by using a
local note.
R6.5
If all fillets and rounds are uniform in size,
dimension may be omitted, but it is necessary to
add the note “ All fillets and round are Rxx. ”
NOTE:
All fillets and round are R6.5
Drawing sheet
R12
unless otherwise specified.
NOTE:
All fillets and round are R6.5

22. f xx
Use leader line and local note to specify diameter
and hole’s depth in the circular view.
HOLES : SMALL SIZE
xx Drill, Thru.
1) Through thickness hole
f xx Thru.
or
xx Drill.
or or

23. f xx, yy Deep
HOLES : SMALL SIZE
or
xx Drill, yy Deep
Hole’s
depth
Use leader line and local note to specify diameter
and hole’s depth in the circular view.
2) Blind hole

24. f xx
Use extension and
dimension lines
Use diametral
dimension line
Use leader line
and note
HOLES : LARGE SIZE

25. COMMON MISTAKE
f xx
f xx f xx
Rxx
f xx
HOLES
f xx

26. CHAMFER
Use leader line and note to indicate linear
distance and angle of the chamfer.
S
S q
For a 45o chamfer
S SCS
or

27. ROUNDED-END SHAPES
R12
f 12
21
5
Dimensioned according to the manufacturing
method used.
Center to Center Distance

28. ROUNDED-END SHAPES
R12
21
5
12
Dimensioned according to the manufacturing
method used.
Center to Center Distance

29. ROUNDED-END SHAPES
Dimensioned according to the manufacturing
method used.
R12
21
12
16

30. ROUNDED-END SHAPES
R12
27
12
Dimensioned according to the manufacturing
method used.
Tool cutting distance

31. ROUNDED-END SHAPES
Dimensioned according to the standard sizes of
another part to be assembled or manufacturing
method used.
25
Key
(standard part)

32. ROUNDED-END SHAPES
Dimensioned according to the standard sizes of
another part to be assembled or manufacturing
method used.
20

33. 1. Extension lines, leader lines should not cross
dimension lines.
POOR GOOD
RECOMMENDED PRACTICE

34. 2. Extension lines should be drawn from the nearest
points to be dimensioned.
POOR GOOD
RECOMMENDED PRACTICE

35. 3. Extension lines of internal feature can cross visible
lines without leaving a gap at the intersection point.
WRONG CORRECT
RECOMMENDED PRACTICE

36. 4. Do not use object line, center line, and dimension
line as an extension lines.
POOR GOOD
RECOMMENDED PRACTICE

37. POOR GOOD
5. Avoid dimensioning hidden lines.
RECOMMENDED PRACTICE

38. POOR GOOD
6. Place dimensions outside the view, unless
placing them inside improve the clarity.
RECOMMENDED PRACTICE

39. JUST OK !!! BETTER
RECOMMENDED PRACTICE
6. Place dimensions outside the view, unless
placing them inside improve the clarity.

40. 7. Apply the dimension to the view that clearly show
the shape or features of an object.
POOR GOOD
RECOMMENDED PRACTICE

41. 8. Dimension lines should be lined up and grouped
together as much as possible.
POOR GOOD
RECOMMENDED PRACTICE

42. 9. Do not repeat a dimension.
POOR GOOD
RECOMMENDED PRACTICE

43. References
• http://www.engineering108.com/pages/Engineering
_graphics/Engineering_graphics_tutorials_free_dow
nload.html
• A text book of engineering graphics- Prof. P.J SHAH
• Engineering Drawing-N.D.Bhatt
• Engineering Drawing-P.S.Gill